CONSTITUTION AND DEVELOPMENT OF TERMITES. 275 
forms as much as two years old (figs. 8 and 9), correspond with 
the interspaces between the first and second, and in succession to 
between the sixth and seventh abdominal somites. The second 
line is usually the widest, but is sometimes similar to the 
others. They occur alike in both sexes, but as the king in- 
creases in bulk less than the queen, they are naturally less 
marked in the former than in the latter sex at the same age 
and never ultimately reach the same degree of accentuation. 
The substitute king and queen are distinguished not alone 
by the almost constant presence of pigment in the compound 
eyes, but also by their pale-yellow colour, which deepens with 
age to a golden tint. 
In these royal forms alike the abdomen becomes enlarged, 
and I have found' examples of both sexes almost equalling 
the largest true kings and queens in size (PI. 16, figs. 12, 13). 
With the natural dilation of the abdomen, certain interseg- 
mental spaces, namely, those which are indicated above for 
the true king and queen, appear as whitish lines. 
I conclude by mentioning that I have looked in vain for 
any difference between the legs of the various forms. The 
tarsi are normally four-jointed; and the apex of the tibia 
possesses three spines, toothed on one side, and common to 
all the legs (Pl. 16, fig. 24). A plantula is present in the 
true imagos, but is wanting in all the other members of the 
colony, including the substitute kings and queens. 
These observations probably hold good for all species of the 
genus Calotermes; I infer this from the many incomplete 
notes which are scattered in the pages of various writers. 
4. Relative Numbers of the Castes. 
A nest contains a single king and queen, neither of which 
can be normally wanting. They may be either true or sub- 
stitute forms. At times one of the pair, either king or queen, 
is a perfect and the other a substitute form; and in such 
cases we have the strange phenomenon of courtship between 
a black and a yellow example. 
The existence of but a single royal couple is an assured 
